Help please!

I posted this on the Yahoo SVX message board where I've been a member for the past 5 years or so, but I haven't received much response other than to run the "self diagnostic test w/the blue wires", but when reading the procedure here, it sounds like it's meant for someone who is having their "Check Engine" light come on and mine is not coming on. I don't have any fault lights coming on in fact. Please please please help me here. Here is the problem I'm having:

My SVX died on me while I was just sitting w/it running parked
eating lunch, and it won't start anymore. It wants to, but won't
catch and start. Originally when it happened, it would catch and
idle very roughly for about 3 seconds and then die again. It has gas and battery power since all the lights etc come on. I've changed out the alternator thinking that it was the problem, but it hasn't changed anything. Please help me if you can. The car seems to crank fine, and like I said all the electrical items come on but it just won't start. Any suggestions? PLEASE.